Back to square 1

Hi i have a daughter shes 2 and a half years old, i potty trained her when she was 27 months old and she was doing perfect where she will tell me each time if she needed to go toilet. But for the past couple of days she want tell me if she needs to go toilet. Its only until she wets her self and then I realise she needs to go. Please help its sooo frustrating thinking that im back to square 1.